My Tire Guide

305/40R18 tire size

A 305/40R18 tire stands 27.6 inches tall and 12.0 inches wide, with a 4.8-inch sidewall on an 18-inch rim.

27.6″OVERALL 27.6 IN · RIM 18 IN12.0″4.8″WIDTH · SIDEWALL
Overall height
27.6 in701 mm
Section width
12.0 in305 mm
Sidewall height
4.8 in122 mm
Rim diameter
18 in457 mm
Circumference
86.7 in2203 mm
Revolutions per mile
731454 per km
Inch size
27.6x12.0R18

Compare it with any other size in the tire size calculator.

Sizes you can swap to

These 18-inch sizes are within two width steps and 3% of a 305/40R18's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 315/40R18, 1.1% taller (0.31 in). Wider sizes also need room in the wheel well and a rim width that suits them.

SizeHeightWidthAt 60 mph
315/40R18+1.1%+0.31 in+10 mm60.7 mph
295/40R18−1.1%−0.31 in−10 mm59.3 mph
285/45R18+1.8%+0.49 in−20 mm61.1 mph
285/40R18−2.3%−0.63 in−20 mm58.6 mph

Plus and minus sizes

Changing rim size means changing the sidewall to keep the same overall height. On 16-inch or 17-inch or 19-inch or 20-inch rims, these are the closest matches to a 305/40R18.

SizeHeightWidthAt 60 mph
295/50R16+0.0%+0.01 in−10 mm60.0 mph
295/45R17−0.6%−0.15 in−10 mm59.7 mph
275/40R19+0.2%+0.06 in−30 mm60.1 mph
275/35R20−0.1%−0.03 in−30 mm59.9 mph

Other 18-inch sizes near 305/40R18

305 mm wide, other sidewalls

40 series, other widths

See the other sizes for this rim on 18-inch tire sizes.

Shop 305/40R18 tires

These open each store's own list of 305/40R18 tires, where you can filter by type, load and speed rating.

305/40R18 questions

How tall is a 305/40R18 tire?

About 27.6 inches (701 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.

What does 305/40R18 mean?

305 is the section width in millimetres (12.0 in). 40 means the sidewall is 40% of that width: 122 mm, or 4.8 in. R means radial construction, and 18 is the rim diameter in inches.

Can I use 315/40R18 instead of 305/40R18?

315/40R18 is 1.1% taller (0.31 in) and 10 mm wider, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 60.7 mph. Make sure the extra width clears the suspension and fender liner at full lock.

What is 305/40R18 in inches?

In inch terms it is 27.6x12.0R18: 27.6 inches tall, 12.0 inches wide, for an 18-inch rim.

How many revolutions per mile does a 305/40R18 make?

About 731 turns per mile, worked out from its unloaded circumference of 86.7 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.